Java example source code file (Basic.java)

This example Java source code file (Basic.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

addrandoms, basic, bytearrayinputstream, bytearrayoutputstream, copy, couldn\'t, element, exception, incorrect, integer, linkedhashset, objectinputstream, objectoutputstream, set, util

The Basic.java Java example source code

/*
 * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/**
 * @test
 * @bug 4245809
 * @summary Basic test for LinkedHashSet.  (Based on SetBash)
 */

import java.util.*;
import java.io.*;

public class Basic {
    static Random rnd = new Random(666);

    public static void main(String[] args) throws Exception {
        int numItr =  500;
        int setSize = 500;

        for (int i=0; i<numItr; i++) {
            Set s1 = new LinkedHashSet();
            AddRandoms(s1, setSize);

            Set s2 = new LinkedHashSet();
            AddRandoms(s2, setSize);

            Set intersection = clone(s1);
            intersection.retainAll(s2);
            Set diff1 = clone(s1); diff1.removeAll(s2);
            Set diff2 = clone(s2); diff2.removeAll(s1);
            Set union = clone(s1); union.addAll(s2);

            if (diff1.removeAll(diff2))
                throw new Exception("Set algebra identity 2 failed");
            if (diff1.removeAll(intersection))
                throw new Exception("Set algebra identity 3 failed");
            if (diff2.removeAll(diff1))
                throw new Exception("Set algebra identity 4 failed");
            if (diff2.removeAll(intersection))
                throw new Exception("Set algebra identity 5 failed");
            if (intersection.removeAll(diff1))
                throw new Exception("Set algebra identity 6 failed");
            if (intersection.removeAll(diff1))
                throw new Exception("Set algebra identity 7 failed");

            intersection.addAll(diff1); intersection.addAll(diff2);
            if (!intersection.equals(union))
                throw new Exception("Set algebra identity 1 failed");

            if (new LinkedHashSet(union).hashCode() != union.hashCode())
                throw new Exception("Incorrect hashCode computation.");

            Iterator e = union.iterator();
            while (e.hasNext())
                if (!intersection.remove(e.next()))
                    throw new Exception("Couldn't remove element from copy.");
            if (!intersection.isEmpty())
                throw new Exception("Copy nonempty after deleting all elements.");

            e = union.iterator();
            while (e.hasNext()) {
                Object o = e.next();
                if (!union.contains(o))
                    throw new Exception("Set doesn't contain one of its elements.");
                e.remove();
                if (union.contains(o))
                    throw new Exception("Set contains element after deletion.");
            }
            if (!union.isEmpty())
                throw new Exception("Set nonempty after deleting all elements.");

            s1.clear();
            if (!s1.isEmpty())
                throw new Exception("Set nonempty after clear.");
        }
        System.err.println("Success.");
    }

    static Set clone(Set s) throws Exception {
        Set clone;
        int method = rnd.nextInt(3);
        clone = (method==0 ?  (Set) ((LinkedHashSet)s).clone() :
                 (method==1 ? new LinkedHashSet(Arrays.asList(s.toArray())) :
                  serClone(s)));
        if (!s.equals(clone))
            throw new Exception("Set not equal to copy: "+method);
        if (!s.containsAll(clone))
            throw new Exception("Set does not contain copy.");
        if (!clone.containsAll(s))
            throw new Exception("Copy does not contain set.");
        return clone;
    }

    private static Set serClone(Set m) {
        Set result = null;
        try {
            // Serialize
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ObjectOutputStream out = new ObjectOutputStream(bos);
            out.writeObject(m);
            out.flush();

            // Deserialize
            ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
            out.close();
            ObjectInputStream in = new ObjectInputStream(bis);
            result = (Set)in.readObject();
            in.close();
        } catch(Exception e) {
            e.printStackTrace();
        }
        return result;
    }

    static void AddRandoms(Set s, int n) throws Exception {
        for (int i=0; i<n; i++) {
            int r = rnd.nextInt() % n;
            Integer e = new Integer(r < 0 ? -r : r);

            int preSize = s.size();
            boolean prePresent = s.contains(e);
            boolean added = s.add(e);
            if (!s.contains(e))
                throw new Exception("Element not present after addition.");
            if (added == prePresent)
                throw new Exception("added == alreadyPresent");
            int postSize = s.size();
            if (added && preSize == postSize)
                throw new Exception("Add returned true, but size didn't change.");
            if (!added && preSize != postSize)
                throw new Exception("Add returned false, but size changed.");
        }
    }
}